1. Field of the Invention
The present invention relates generally to an ignition coil control device and more particularly to an ignition control device for regulating the optimal conduction time of the coil for an internal combustion engine.
2. Description of the Prior Art
In the traditional ignition system, the spark causing the ignition of the explosive mixture contained inside a cylinder of an internal combustion engine is produced by a burst of electric current circulating in the primary circuit of a coil. This burst produces an overvoltage in the secondary circuit which is connected to the spark plugs. The primary electric circuit of the coil must then remain closed for a sufficient time to restore the current necessary to obtain the required energy in said coil.
In so-called transistorized ignitions where the traditional burst mechanism is replaced by a position sensor which controls a power transistor, the primary circuit opening time remains constant and is equal to the minimum time needed to produce a spark. This solution, as well as the traditional solution, presents a major inconvenience at slow speed since the current consumed is greater than to the current strictly necessary to restore sufficient energy to the coil.
Another solution provides for controlling the coil at a constant operating time regardless of the rotational speed of the engine. If this time is exactly equal to the necessary coil recharge time, the ignition circuit consumes the minimum amount of current. One solution of this type applied to a "totally electronic" ignition, where the power transistor system is controlled by a calculator which determines at each moment the angle of ignition advance, is the object of the French Pat. No. 2,358,564, filed on July 15, 1976 under the name of Regie nationale des usines RENAULT for a "constant conduction time control device for a combustion motor ignition coil". This solution is adapted to all types of electronic ignition advance calculators and presents the advantage of adjusting the constant conduction time parameters aided by the use of a programmable logic array (PLA). But the problem that is resolved by this patent application involves a number of parameters reduced to attain the least expensive solution and also relates to the immunity of the device in regard to the acceleration constraints which the solution must be able to tolerate.